JPS6398670A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To faithfully transfer a multicolor toner image without any image disorder and to obtain a multicolor image which has neither color blurring nor character blurring by providing an exposing device in front of a transfer part, further arranging a conductive transparent electrode between the exposing device and a photosensitive body, and applying a voltage having the same polarity with toner simultaneously with exposure. CONSTITUTION:An electrostatic charger 41, an image exposing device 37, and developing devices 43-35 are arranged along a movement surface for the photosensitive body, a before- transfer exposing device L, a transfer electrode 50, and a separation electrode 51 are arranged, and recording paper which is separated here is fixed by a fixing unit 52. Remaining toner which sticks on the photosensitive body is removed by a cleaning device 46. When a multicolor image is formed, the image exposure of the 1st color component is performed, development is carried out with corresponding toner to form a toner image on the surface of the photosensitive body 40, and then a next copying cycle is entered without before-transfer exposure, operation of a transfer separation electrode, cleaning, etc. Then plural toner images are formed one over another on the photosensitive body 40 successively to form a multiple or multicolor toner image. The final toner image is formed on the photosensitive body and then the before-transfer exposure is carried out and the image is transferred to recording paper by a transfer electrode, an the recording paper is separated from the photosensitive body 40 by a separation electrode 51 and fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multicolor image forming apparatus, and more particularly to a multicolor image forming apparatus using an electrophotographic method.

(Prior art) Multicolor image forming apparatuses include wire tod matrix recording method, inkjet recording method, thermal transfer recording method,
There are electrostatic recording methods, electrophotographic recording methods, etc. In the electrophotographic recording method, it is difficult to downsize the device because it requires multiple developing devices that handle photoreceptors, powder, or liquid;
It has the advantage that a resolution of /zx or higher can be easily obtained and can be recorded at high speed. With other methods, it is difficult to stably obtain such high resolution.

There are various methods for recording multicolor images using electrophotography.
The method called full color process separates the original image into three colors: blue (B), green (G), and red (R), and exposes each color separately to a photoreceptor to produce yellow (Y), magenta (M),
Cyan (C) (black if necessary) development is performed, and toner images are transferred one color at a time onto pine paper to obtain a full-color image. Further, as an electrophotographic method for color hard copies, there is one disclosed, for example, in Japanese Patent Application Laid-Open No. 144452/1983. In this case, there are multiple exposure devices and developing devices for each color on the circumference of the photoreceptor, and by transferring the images onto recording paper at once, it is possible to obtain one multicolor hard copy per rotation of the photoreceptor. . Furthermore, in the above example, the image is written using multiple exposure Vcras, but examples in which this is done using one laser exposure device are disclosed in Japanese Patent Laid-Open No. 60-75850 and No. 60-76766.
It is disclosed in the publication No. However, in this case, the photoreceptor needs to be rotated multiple times.

The above method performs color reproduction by separating the three primary colors (B%G, R) for image formation, but in contrast to this, there is a slightly special method that separates the colors into two colors and reads them. Several methods for obtaining signals have been disclosed. Examples include JP-A-56-162755 and JP-A-57-44825.

(Problems to be Solved by the Invention) In the electrophotographic multicolor image forming apparatus as described above, there are problems that have not been experienced with monochrome electrophotographic copying machines, and it is difficult to always produce stable multicolor images. It was difficult to obtain with good reproducibility. In an electrophotographic copying machine, the toner image formed on the photoreceptor is transferred to recording paper, and when it is separated, the potential of the photoreceptor can be erased by exposing it to light before the transfer, which improves the transfer rate and further improves the transfer rate. The surface potential of the photoreceptor before transfer is uniform and stable, and stable RFP electrical separation performance can be obtained against changes in paper quality and environment. Multicolor image forming apparatus such as JP-A-60-206692 and JP-A-60-16
The above-mentioned pre-transfer exposure is also effective in the method described in Japanese Patent No. 6549, in which multiple or multi-color toner images are formed on a photoreceptor and transferred at once; however, in this case, we An image problem unique to this technique called exposure flickering (hereinafter simply referred to as flipping) has occurred. This phenomenon is a phenomenon in which toner scatters around the image and blurs the image and characters, making it impossible to obtain good images and characters. It is necessary to make it possible. That is, an object of the present invention is to provide an image forming apparatus that firstly transfers a multicolor toner image faithfully without image holes and obtains a multicolor image without color bleeding or character bleeding by solving the problem of repelling. This is Shiroko. The second object is to provide an image forming apparatus that can maintain a high transfer rate of toner of each color regardless of environmental changes and changes in paper quality, and can produce multicolor images with high density and vivid colors. A third object is to provide a multicolor image forming apparatus which assists and reliably performs electrostatic separation of recording paper from a photoreceptor and has high feeding reliability.

(Means for Solving the Problems) The object of the present invention is to improve the transfer of photoreceptors! ! ! An electrostatic image forming means and a plurality of developing devices are provided along the LJ surface, and after forming a power-saving image and developing it multiple times to form a multiple or multicolor toner image on the photoreceptor, the toner image is transferred onto the recording paper. In a multiple copying or multicolor copying device that transfers e'IrL at one time and then cleans the remaining silver on the photoreceptor, an exposure device is provided before the transfer section, and a conductive device is provided between the exposure device and the photoreceptor. This can be achieved by using a multicolor image forming device that has transparent electrodes and applies a voltage of the same polarity as the toner at the same time as the exposure. Further, by providing an AC corona charge removal/separation device after the electrostatic transfer device that removes the static charge on the recording paper by AC corona discharge and separates the recording paper from the photoreceptor together with the toner image, good transfer and separation performance can be obtained. An example of the mechanism of the multicolor image forming apparatus according to the present invention is shown in the first example.
As shown in the figure. A is a read unit and B is a write unit.

A charger 41 and an image exposure device 37 are installed along the moving surface of the photoreceptor.
, developing units 43, 44, and 45, and further provided with a pre-transfer exposure device WIL, a transfer pole 50, and a #l pole 51, where the separated recording paper is fixed by a fixing unit 52.

The remaining toner attached to the photoconductor is removed by cleaning device W14.
In forming a multicolor image in the present invention, first, image exposure of a first color component (for example, red) is carried out, and this is developed with a corresponding toner (for example, cyan), and the toner image is transferred to a photoreceptor. Form on the surface. Then, pre-transfer exposure,
The next copy cycle begins without being affected by transfer separation poles, cleaning, etc. In this way, a plurality of toner images of red, black, etc. are sequentially superimposed on the photoreceptor to form a multiple or multicolor toner image. After forming an af& toner image on the photoconductor, the pre-transfer exposure is performed, the transfer pole transfers the recording paper to the recording paper, the 1% pole separates the recording paper from the photoconductor, and the multicolor image is fixed. Copies can be made. Considering the effect of pre-transfer exposure in such a mechanism, if the conventional method of exposing the photoconductor surface using a pre-transfer exposure device is used, the multilayer or multilayer structure formed on the photoconductor by development will be The amount of light reaching the photoreceptor surface changes due to the influence of the transmittance due to the presence of colored toner images, and the degree of potential reduction of the photoreceptor itself varies. This creates a situation where the potential of the photoreceptor in the area where toner is attached becomes higher than the potential of the photoconductor in the area where toner is not attached, and as a result, the toner flies due to the action of electric lines of force generated around the toner image, and the image or This is thought to be a phenomenon in which characters bleed. Therefore, as a result of various studies, the present inventors discovered that toner flying can be suppressed by applying a voltage with the same polarity as the toner at the same time as the pre-transfer exposure. We invented a method in which light is irradiated through an electrode and exposed while applying a voltage. Picture quality degradation and transparency? [
The relationship between the applied voltage and the applied voltage is shown. In the figure, the vertical axis represents the degree of image quality deterioration, the horizontal axis represents the applied voltage, and the gap d between the electrode and the photoreceptor was changed. The degree of image quality deterioration was determined by visually evaluating the degree of image blurring mainly due to flickering, with 1 being good and 5 being extremely poor. Practically speaking, the limit is about 2. As shown in the figure, image quality deterioration can be clearly prevented by applying a voltage. However, d is 1 mx-0
, 3xz, and the applied voltage is preferably 0.8Kv-1.5V. If the electric field between the photoreceptor and the electrode exceeds 3 Kv/zy, there is a risk of air discharge.The present invention can suppress the generation of electric lines of force that cause toner to fly, and solve the repelling problem. done. Then, after being transferred by electrostatic transfer, etc., it is recorded by AC corona discharge! By removing the e-charges on the paper, the transfer ability and separation ability were increased together with the original effect of pre-transfer exposure, and it was possible to obtain a good multicolor image copy with high resolution and no character blurring.

Examples of photoreceptors used in the present invention include selenium-based, organic compound-based, amorphous silicon-based, titanium oxide-based,
There are zinc oxide types, etc. However, there are many types of compounds with various properties, and organic compounds are superior in the sense that they have an extremely wide range of choices. Among these, a desirable organic compound-based photosensitive material must be sensitive to semiconductor laser light and have sufficient color sensitivity in the red to infrared range. Specifically, for example, Japanese Patent Application Laid-Open No. 59-21844
Azo pigments such as those described in Publication No. 7 or JP-A-5
9-219752, JP 59-214034, JP 59-155851, JP 59-155847
No., JP-A-55-59468, JP-A-54-1478
A 7-thalocyanine compound or complex as described in Japanese Patent Publication No. 39 is used as a charge-generating substance, and a tri-7-arylamine derivative as described in JP-A-61-14642 is used as a charge transporting substance. For example, when creating an actual photoreceptor, Vf
It is preferable to use the layer structure or *side technique described in publications such as JP-A No. 2-135736, JP-A No. 53-44028, JP-A-53-76036, and Vf No. 53-58240.

Developers used in the present invention On the other hand, there are two types of developers used in such a multicolor image forming apparatus: a two-component developer consisting of toner and a carrier, and a one-component developer consisting only of toner. be. Two-component developers require control of the amount of toner relative to carrier, but have the advantage that triboelectric charging of toner particles can be easily controlled.

In addition, especially in a two-component developer composed of a magnetic carrier and a non-magnetic toner, it is not necessary to contain a large amount of black magnetic material in the toner particles, so it is possible to use color toner that does not cause color turbidity due to the magnetic material. It has the advantage of being able to form clear color images.

It is particularly preferable that the two-component developer used in the present invention is composed of a magnetic carrier as a carrier and a non-magnetic toner as a toner.

It is preferable to use carrier particles with an average particle size of about 5 to 80 μl, and most preferably a layer of 5 to 40 μl.

In addition, the toner particle size should preferably have an average particle size of about 1 to 20 μl,
3-15 μl is most desirable.

Examples of these developers include, for example, Japanese Patent Application Laid-Open No. 53-83
No. 60, Patent Application No. 1982-129213, Patent Application No. 1987-1
No. 07452, Japanese Patent Application No. 59-134078, Japanese Patent Application No. 1983
It is described in publications such as Japanese Patent Application No. 9-125283, Japanese Patent Application No. 59-129215, Japanese Patent Application No. 59-129216, and Japanese Patent Application No. 129217.

As the bindu resin in the present invention, various thermoplastic resins can be used, including addition polymerization type resins such as styrene resin, styrene-acrylic resin, styrene-butanoene resin, and acrylic resin, polyester resin,
Examples include condensation polymerization resins such as polyamide resins, and epoxy resins.

The materials constituting the toner include (1) thermoplastic resin: binder 80-90m1% e.g. polystyrene, styrene acrylic polymer, polyester,
Polyvinyl butyral, epoxy resin, polyamide II
N, polyethylene, ethylene-vinyl acetate copolymer, etc. or mixture of the above (2) Pigment: Colorant 0-15 wL% Example: Black: Carbon black Anne: Copper 7 talocyanine, sulfonamide derivative dye Yellow: Bennone derivative 1 Magenta: Rhodamine B Lake, Carmine 6B, etc.

(3) Charge control agent O~5wL% Positive donor: Nigrosine-based electron-donating dyes, alkoxylated amines, alkylamidochelates, pigments, quaternary ammonium salts, etc.

Negative toner Two-electron accepting organic complex, chlorinated paraffin, chlorinated polyester, polynystyl with excess acid groups. Chlorinated f: i47 talocyanine, etc.

(4) Examples of fluidizing agents: coroiglu silica, hydrophobic silica, silicon face, metal soap, nonionic surfactants, etc.

(5) Cleaning agent (prevents toner filming on the photoreceptor) Examples: fatty acid metal salts, oxidized silicic acid with organic groups on the surface, fluorine surfactants, etc.

(6) Fillers (aimed at improving the surface gloss of images and reducing the amount of raw materials used) Examples: calcium carbonate, clay, talc, pigments, etc.

In addition to these materials, a magnetic material may be included to prevent fogging and toner scattering.

As the magnetic powder, 0.1 to 1 μl of triiron tetroxide, γ-ferric oxide, chromium dioxide, nickel 7-elite, iron alloy powder, etc. are used, and the content is 5 to 70 wt % based on the toner.

The resistance of the toner varies considerably depending on the type and amount of magnetic powder, but in order to obtain a sufficient resistance of 101 Ωcm, preferably 10 Ωcm or more, it is preferable to keep the amount of magnetic material below 55 wt%. In order to maintain a clear color as a toner, the amount of magnetic material is desirably 30-t% or less, and particularly desirably 5% or less.

Suitable resins for pressure fixing toners that plastically deform and adhere to paper with a force of approximately 20 Ay/ax include adhesive resins such as wax, polyolefins, ethylene-vinyl acetate copolymers, polyurethane, and rubber. It will be done. Capsule toners can also be used.

A toner can be made using the above-mentioned materials by a conventionally known manufacturing method.

In the structure of the present invention, in order to obtain a more preferable image, it is desirable that the particle size (weight average particle size) of these toners is about 50 μl or less.

In the multicolor image forming apparatus of the present invention, there is no theoretical limit to the toner particle size, but from the viewpoint of resolution, toner scattering, and conveyance, it is usually preferably about 1 to 30 μm, but 3 to 15 μm.
The weight average particle size is particularly preferred, and the weight average particle size is the value measured with a Coulter Counter manufactured by Coulter.

Next, in the present invention, the transparent electrode to which the voltage of the same polarity as the toner is applied to the pre-transfer exposure area is positioned in front of the transfer pole 50 in FIG. 1, and in order to perform the pre-transfer exposure and voltage application simultaneously. can have a structure as shown in the fjS2 diagram. That is, a tungsten lamp array 81 including, for example, seven LEDs, fluorescent lamps, and tungsten lamps is arranged in the lamp house 82 so that the surface of the photoreceptor 40 can be exposed to light through the slit of the light-shielding plate 85.

A transparent conductive electrode 84 made of Nesa glass is provided in front of the lamp house and in front of the light-shielding plate, and a groove is formed between it and the photoreceptor so that a voltage of the same polarity as that of the toner can be applied.

The static elimination lamp for pre-transfer exposure may be operated so as to be turned on immediately before the multicolor toner image passes through the lamp section, and turned off when the trailing edge of the image has finished passing through. In this case, the amount of light from the lamp is approximately 5 to 10 times the amount of light that would normally reduce the surface potential of the photoreceptor, which is about -800 V after recharging, to about -100 V. With this amount of light, the potential of the photoreceptor below the black toner can be sufficiently erased to below -100V.

In general, organic photoreceptors for semiconductor lasers require 2.
5-5. Oluxsec, so the exposure is 7
．． It requires 5Luxsee -50Luxsee.

At the same time as this exposure, a voltage of the same polarity as that of the toner is applied using a transparent electrode made of Nesa glass. The distance between this Nesa glass and the photoreceptor is 0.311 to 1. Or shoulder is desirable,
In order to maintain this distance accurately, spacers made of a material with low frictional resistance, such as tear iron or polyacetal, should be placed on both sides of the Nesa glass and rubbed against the drum surface.

The voltage applied between the photoreceptor and Nesa Glass is 0.8KV
-1°5KV. Note that the electric field in the gap is 3. OKV/z
If it exceeds z, there is a risk of air discharge, so it is necessary to keep it within that range.

Also, is the separation electrode for transfer? ! Along with the pole, it is a road sign.

Each of them is composed of a discharge wire, and the transfer wire applies a DC voltage and the separation wire applies an AC voltage of several KV between it and the photoreceptor substrate.

(Example) Example 1 FIG. 1 shows the configuration of a multicolor image forming apparatus according to the present invention, and a multicolor image is formed in the following manner.

In FIG. 1, A is a reading unit, B is a writing unit, C is an image forming section, and D is a paper feeding section.

In reading unit A, 1 is a platen plus, and an original 2 is placed on this platen glass 1. Manuscript 2 is
It is illuminated by fluorescent lamps 5 and 6 provided on a carriage 4 that moves on a slide rail 3. The movable mirror unit 8 is provided with mirrors 9 and 9', which move on the slide rail 3, and in combination with the first mirror 7 provided on the carriage 4 read the optical image of the document 2 on the platen glass 1 with a lens. Derived to unit 20.

The lens reading unit 20 includes a lens 21. prism 22
, the first reading board 24, the red channel (hereinafter R-
ch) CCD 25, tt%2 reading board Z6,
Cyan channel (hereinafter referred to as C-cb) CCD 27
It consists of The original optical image transmitted by the Pt51 mirror 7, mirror 9, and mirror 9' is focused by a lens 21, and separated into an R-ch image and a C-Ch image by a gicroic mirror provided in a prism 22. tIS
l R-Ch CCD 2 provided on the reading board 24
5 and C-Ch C provided on the second reading board 26
The images are respectively formed on the light receiving surface of the CD 27.

Said R-ch CCD 25 and C-ch CCD 2
The image signal output from 7 is subjected to signal processing in a signal processing section E, which will be described later. In the signal processing section E, a color signal separated according to the color of the toner, which will be described later, is outputted and inputted to the writing unit.

Writing 22) In B, a laser beam generated by a semiconductor laser is rotated and scanned by a polygon mirror 32 rotated by a drive motor 30, and is reflected via an Fθ lens @3
7, the optical path is bent, and the photosensitive drum 40, which has been uniformly charged in advance by an electric device 41, is scanned. During the main scanning by the laser beam and the sub-scanning by the rotation of the photosensitive drum 40, a latent image corresponding to the first color is formed on the drum surface. This latent image is developed by a developing device 44 loaded with red toner, for example, to form a toner image on the drum surface. The obtained toner image passes under the cleaning device W146, which is separated from the photosensitive drum surface, while being held on the drum surface, and enters the next copy cycle. The photosensitive drum 40 is charged again by the charger 41.

Next, the Pt52 color signal output from the signal processing section E is input to the writing unit B, and is written on the drum surface to form a latent image in the same manner as in the case of the fjSl color signal. The latent image is developed by a developer 45 loaded with toner of a second color, for example blue. This blue toner image is formed over the already formed red toner image.

A developing device 43 has black toner and forms a black toner image on the drum surface based on a control signal generated by a signal processing section. AC and DC biases are applied to the sleeves of these developing devices 43, 44, and 45 to perform no-yumping development with two-component toner, and non-contact development is performed on the grounded photosensitive drum 40. In this embodiment, the toner images are stacked in the order of black, red, and blue. The superimposed image of toner images developed with black, red, and blue toners in this way is exposed to pre-transfer exposure vcr! 1 and VcrIIL consisting of a conductive transparent electrode, the toner is exposed to light and a voltage of the same polarity as that of the toner is applied at the same time. Next, the image is transferred by the transfer pole 50 onto the recording paper 61 fed by the feeding belt 62 and feeding row 263 of the paper feeding section. The transfer paper on which the toner image has been transferred is separated from the photoreceptor by a separation pole 51 by AC corona discharge, and further conveyed to a fixing device 52 where it is fixed and a color hard copy is obtained.

A cleaning device 46 comes into contact with the photosensitive drum 40 after the transfer, and performs cleaning with a blade 47 to remove unnecessary toner from the drum surface.

The roller 49 of the cleaning device is used to remove a small amount of toner left behind between the drum surface and the blade when the blade 4f is separated from the drum surface in preparation for the next exposure and development after cleaning. , while rotating in the opposite direction to the drum, rubs the contact portion with the drum surface to collect residual toner.

The image forming conditions in the multicolor image forming apparatus of this example were as follows.

Image forming conditions (1) Image forming member photosensitive layer Organic photosensitive layer consisting of a charge generating substance 7 talonamine compound and a charge transporting substance triaryl 7 amine derivative Drum diameter 1400 Linear speed
58az/sgc surface potential Charging potential (potential of non-image area during development) -650V exposure area potential -10V image exposure conditions Light source Semiconductor laser wavelength 780±20nm 1i density 16dots/zi Developing device sleeve Non-magnetic stainless steel, 180uφ line speed 20
Rotating magnet with z*/see 8 poles, rotating magnetic flux density 7X70 with 600 rpm
(Lus (sleeve surface) developer carrier Magnetic powder resin dispersion system, average particle size (weight basis) 20 μl Specific resistance 1014 Ω CC shoulder magnetization approximately 50 emu/g (σ10011) σ1°.

:100 (magnetization in a magnetic flux density of 1 s) Red (R) Average particle size (weight basis) 11 μl Average charge 110 μc/g (toner concentration 15 wt%) Disperse a-damin B lake.

Blue (B) Average particle size (weight basis) 11 μl Average charge amount 12 μc/g (toner concentration 15 wt%) Carbon black is dispersed.

Black (K) Average particle size (weight basis) 11μ Summer average charge flL12μc/y (toner concentration 15wt%) Carbon black is dispersed.

Development conditions Between photoreceptor and sleeve 1,0xm Development scrap thickness 0.2~0.8z Shoulder (quiet) (Regulated by non-magnetic blade) (Common to the above) Development bias (black) DC-500VAC1,0KV (effective value )
2KIIz (red) DC-500VAC1,0KV
(Effective value) 2Kllz (blue) DC-500VA
CO, 8KV (effective value) 2KIIz Pre-transfer exposure conditions Tungsten lamp array used 30 Luxsec Voltage applied by transparent electrode -1, OKV transfer voltage ff
l DC4,8KV separation electrode
AC 3.6 KV (both voltages applied between the wire and the drum base) According to this example, in the case of the present invention, good copies could be obtained without blurring of images and characters.

Example 2 Example 1 was a multicolor image using three color toners, but R (Y), magenta (M), cyan (C), black (B) described in JP-A-60-208692 was used. ) describes an example of simultaneously transferring a multicolor image formed by overlapping four color toners, and plS3 shows the Ps of the multicolor image forming apparatus,
In this embodiment, a conductive transparent electrode according to the present invention is used, and a good result is obtained by applying the method of the present invention in which a voltage of the same polarity as that of the toner is applied from the surface of the photoreceptor at the same time as the pre-transfer exposure. I was able to get a copy.

(Effects of the Invention) As explained in detail in the Examples and clarified, in the multicolor image forming apparatus according to the present invention, which forms multicolor or multiple toner images on a photoreceptor and transfers them onto recording paper at once,
Color turbidity in each color without damaging the toner image,
It was possible to form a multicolor image with high density and no color bleeding. ! It was possible to form a good character image with high resolution and no character bleed. Furthermore, the present invention provides a multicolor image forming device that can always form a clear multicolor image with sufficient density even under changes in the environment and paper quality, and has high feeding reliability with less winding of recording paper. It happened.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of a multicolor image forming apparatus shown in Example 1 of the present invention, and the ttSZ diagram is a sectional view of the Naro apparatus including a transparent electrode and a pre-transfer exposure lamp. FIG. 3 is a schematic diagram showing the configuration of a multicolor image forming apparatus according to Example 2 of the present invention, and FIG. 4 is a diagram showing the relationship between voltage applied to a transparent electrode and image quality deterioration according to the present invention. A: reading unit), B: writing unit, C: image forming section, D: paper feeding section, 40: photoreceptor, 51: static elimination separation device, 81;
Tungsten lamp 84: Transparent electrode L: Cross-sectional view of a device consisting of a pre-photography exposure lamp and a transparent electrode Applicant: Konishiroku Photo Industry Co., Ltd. Figure 1

Claims (2)

[Claims] (1) An electrostatic image forming means and a plurality of developing devices are provided along the moving surface of the photoreceptor, and electrostatic image formation and development are performed multiple times to form multiple or multicolor toner images on the photoreceptor. After forming,
In a multiple copy or multicolor copying device that performs electrostatic transfer onto recording paper at one time and then cleans toner remaining on the photoconductor, an exposure device is provided before the transfer section, and an exposure device is provided between the exposure device and the photoconductor. A multicolor image forming apparatus characterized in that a conductive transparent electrode is provided and a voltage of the same polarity as that of the toner is applied simultaneously with the exposure. (2) The invention further comprises an AC corona charge removal/separation device which removes the static charge on the recording paper by AC corona discharge after the electrostatic transfer device and separates the recording paper from the photoreceptor together with the toner image. 2. The multicolor image forming apparatus according to item 1.